Evidence of pre-late Wisconsinan glaciations on Labrador Shelf – Cartwright Saddle region

Abstract

High-resolution Huntee and air-gun seismic reflection profiles from Cartwright Saddle indicate the presence of at least three major glacial advances, which deposited giacial till sequences up to 100 m in composite thickness on the bottom and flanks of the saddle. These tills are found in water depths up to 600 m, and their acoustic character suggests deposition from grounded ice. Grounded ice at such depths and the presence of tills extending to the shelf edge indicate major glacial episodes. A combination of surface morphology and high-resolution seismic profile data reveals the presence of an extensive lateral moraine that flanks the southern edge of the saddle, suggesting that an ice tongue filled the saddle. Numerous areas of pinch-out of the upper till are recognized along the lateral moraine and near the shelf edge. In the deepest part of the saddle, high-resolution seismic records across a core site obtained earlier by Vilks show the core penetrates the upper part of a postglacial stratified silt sequence overlying glacial till. Extrapolating the 14C date obtained by Vilks from this core suggests the minimum date for the underlying till is approximately 70 000 years BP. Thus there is no indication of late Wisconsinan till in the area.